The phase demodulation angles are numerical values that are stored in the micromachine firmware. During normal operation, these parameters are used by the digital electronics of the microsensor to govern the operation of the signal processing that they implement. Empirical evidence has revealed that a significant source of poor performance (i.e. the rate bias hysteresis) will change depending on the phase demodulation angles used in the digital signal processing of the system.
Accordingly, there is a need in the art of micromachined devices to provide methods for improving their performance by minimizing the rate bias hysteresis.
It is an object of the invention to provide methods to improve the performance of micromachined devices.
It is another object of the invention to minimize the rate bias hysteresis over temperature of micromachined devices, preferably angular rate microsensors.
It is another object of the invention to provide methods of optimizing phase demodulation angles at which the bias hysteresis over temperature is minimized.
The present invention provides a method for improving the performance of a micromachined device having at least one sensing element and capable of producing a frequency modulated signal. The micromachined device is preferably a silicon microsensor that can measure angular rate and/or linear acceleration of a moving object. The sensing element of the microsensor can be at least one tine having a rate bias used for determining a rate bias hysteresis over temperature. The performance of the micromachined device is improved by determining at least two phase demodulation angles at which the rate bias hysteresis over temperature is at a minimum.
The present invention also provides a micromachined device having at least one sensing element, wherein the rate bias hysteresis over temperature of the sensing element has been minimized by using the method of generating optimum phase demodulation angles according to the method of the present invention.
As a result of the present invention a unique method of obtaining and reducing data from a micromachined sensor that can be utilized to derive phase demodulation angles that minimize the bias hysteresis is provided. This method produces an optimum set of phase demodulation angles. The data collection method involves the collection of rate bias data over temperature using various phase demodulation angle settings. The subsequent data reduction method involves the minimization of the rate bias hysteresis over temperature using methods of dynamic programming optimization.
Other improvements which the present invention provides over the prior art will be identified as a result of the following description which sets for the preferred embodiment of the present invention. The description is not in any way intended to limit the scope of the present invention, but rather only to provide a working example of the present preferred embodiments. The scope of the present invention will be pointed out in the appended claims.